SP7685
1.2A Buck/Boost Charge Pump LED Driver
FEATURES
■ Output Current up to 1.2A
■ Up to 94% Efficiency in Torch Mode
■ Adjustable FLASH Mode Current
■ Minimum External Components: No Inductors
■ Automatic Buck/Boost Mode Switchover
■ Wide VIN Range: 2.7V to 5.5V
■ High Frequency Operation: 2.4 MHz
■ 50mV Reference for low Loss Sensing
■ IQ < 2μA in Shutdown
■ PWM Dimming Control
■ Automatic Soft Start Limits Inrush Current
■ Overvoltage Protection on Output
■ Overcurrent/temperature Protection
■ Low Ripple and EMI
■ Ultra-low Dropout Voltage in Buck Mode
■ 2.6 Second Timeout in Flash Mode
■ Space Saving RoHS Compliant, Lead Free
Package: 10-pin 3mm x 3mm DFN
VIN
1
C1
2
SP7685
C2
3
10 Pin DFN
FLASH
EN
10
VOUT
9
PGND
8
SGND
4
7
FB
5
6
RSET
APPLICATIONS
■ White LED Torch/Flash for Cell
Phones, DSCs, and Camcorders
■ White LED Backlighting
■ Generic Lighting/Flash/Strobe
Applications
■ General Purpose High Current Boost
DESCRIPTION
The SP7685 is a current-regulated charge pump ideal for powering high brightness LEDs for
camera flash applications. The charge pump can be set to regulate two current levels for
FLASH and TORCH modes. The SP7685 automatically switches modes between step-up
and step-down ensuring that LED current does not depend on the forward voltage. A low
current sense reference voltage (50mV) allows the use of small 0603 current sensing
resistors. The SP7685 is offered in 10-pin DFN package.
TYPICAL APPLICATION CIRCUIT
VIN
(3.0 - 4.2V)
O
CIN
10μF
VIN
CFC
1μF
TORCH/FLASH
ENABLE
¤
VOUT
COUT
10μF
C1 SP7685 PGND
C2
SGND
FLASH
FB
RSET
EN
RSET
80KΩ
Date: 6/20/06 Rev T
1A Flash
200mA Torch
PWF1 WLED
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
1
RSENSE
0.22Ω
© 2006 Sipex Corporation
ABSOLUTE MAXIMUM RATINGS
VIN , VOUT ....................................................................... -0.3V to 6V
Output Current Pulse (Flash) ................................. 2A
Output Current Continuous (Torch) ..................... 0.4A
Storage Temperature ...................... -65°C to +150°C
Operating Temperature ..................... -40°C to +85°C
VEN ............................................................ 0.0V to 7V
3x3 10 DFN .........................................OJA = 40.5°C/W
ESD Rating. ................................................ 2kV HBM
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect
reliability.
ELECTRICAL CHARACTERISTICS
TA = -40°C to +85°C, VIN =3.6V, CIN = 10μF, CFC =1.0μF, COUT =10μF. VSHDN = VIN, typical values at 25°C. The
♦ denotes the specifications which apply over the full operating temperature range unless otherwise noted.
PARAMETER
Operating Input Voltage
MIN.
TYP.
2.7
Quiescent Current
0.5
MAX.
UNITS
CONDITIONS
5.5
V
♦
3
mA
♦
2
Shutdown Current
FLASH = High, 2x mode
2
Oscillator Frequency
V IN = 2.7 - 5.5V FLASH = GND,
1X Mode, ILOAD = 100μA
μA
V IN = 5.5V, VEN = 0.0V
2.4
MHz
Charge Pump Equivalent
Resistance (x2 mode)
4
Ω
V FB = 0.0V, V IN= 3.6V
Charge Pump Equivalent
Resistance (x1 mode)
0.4
0.7
Ω
V IN = 3.6V
45
50
55
mV
♦
FLASH = GND
138
150
162
mV
♦
FLASH = High, R SET = 53.6kΩ .
400
mV
♦
FLASH = High. Guaranteed by design.
FB Pin Current
0.5
μA
EN, FLASH Logic Low
0.4
V
♦
V
♦
0.5
μA
♦
500
μs
♦
V IN = 3.6V, FB within 90% of
regulation
♦
FLASH = High
FB Reference Voltage
FB Reference Voltage Range
EN, FLASH Logic High
100
1.3
EN, FLASH Pin Current
V OUT Turn-on Time
170
Thermal Shutdown
Temperature
145
Maximum Flash ON time
Date: 6/20/06 Rev T
1.6
2.6
o
3.6
V FB = 0.3V
C
s
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
2
© 2006 Sipex Corporation
PIN DESCRIPTION
PIN
PIN NAME
NUMBER
DESCRIPTION
1
VIN
Input Voltage for the charge pump. Decouple with
4.7µF ceramic capacitor close to the pins of the IC.
2
C1
Positive input for the external flying capacitor. Connect
a ceramic 1µF capacitor close to the pins of the IC.
3
C2
Negative input for the external flying capacitor. Connect
a ceramic 1µF capacitor close to the pins of the IC.
FLASH
Logic input to toggle operation between FLASH and
TORCH mode. In TORCH mode FB is regulated to the
internal 50mV reference. In FLASH mode FB reference
voltage can be adjusted by changing the resistor from
RSET pin to ground. Choose the external current sense
resistor (R SENSE) based on desired current in TORCH
mode. This pin does not have an internal pull-up/pulldown; do not leave this pin floating.
4
5
EN
6
RSET
7
FB
8
SGND
9
PGND
10
VOUT
Date: 6/20/06 Rev T
Shutdown control input. Connect to VIN for normal
operation, connect to ground for shutdown. This pin
does not have an internal pull-up/pull-down; do not
leave this pin floating.
Connect a resistor from this pin to ground. When in
FLASH mode (FLASH = High) this resistor sets the
current regulation point according to the following: VFB =
RSET*14uA/5 (Flash Mode)
Feedback input for the current control loop. Connect
directly to the current sense resistor.
Internal ground pin. Control circuitry returns current to
this pin.
Power ground pin. Flying capacitor current returns
through this pin.
Charge Pump Output Voltage. Decouple with an
external capacitor. At least 1µF is recommended.
Higher capacitor values reduce output ripple
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
3
© 2006 Sipex Corporation
FUNCTIONAL DIAGRAM
CLK
RSET BLOCK
RSET 6
+
RSET
RSET REF=
{ }
RSET
5
RSET REF
BG REF
+
- 1.26V
RESISTOR
TAPS
COUNTER
32 COUNT
FB REF
1
MUX
2x1
50mV 0 s
+
-
FB 7
FB COMP
FB
COM P
SGND 8
x 14μA
FLASH 4
FLASH=1, S=1, RSET REF
FLASH=0, S=0, 50mV
SET
DOMINANT
S
0
CLR
ONE
SHOT
R
EN 5
VIN 1
MODE SWITCH
0 =1X
1=2X
135C ON
THERMAL FAULT
OVER TEMP COMP
145C OFF
2.4MHZ
CLK
CHARGE
PUMP
SWITCHES
C1
C2
VOUT
CLK
PGND
THEORY OF OPERATION
The SP7685 is a charge pump regulator
designed for converting a Li-Ion battery
voltage of 2.7V to 4.2V to drive a white LED
used in digital still camera Flash and Torch
applications. The SP7685 has two modes
of operation which are pin-selectable for
either Flash or Torch. Flash mode is usually
used with a pulse of about 200 to 300
milliseconds to generate a high intensity
Flash. Torch can be used continuously at a
lower output current than Flash and is often
used for several seconds in a digital still
camera “movie” mode.
acts like a linear regulator to control the
output current by continuously monitoring
the feedback pin FB. In 1X mode, if the
SP7685 auto detects a dropout condition,
which is when the FB pin is below the
regulation point for more than 32 cycles of
the internal clock, the SP7685 automatically switches to the 2X mode. The SP7685
remains in the 2X mode until one of four
things happens: 1) the enable pin EN has
been toggled, 2) the Flash pin has changed
from high to low, 3) VIN is cycled or, 4) a
thermal fault occurs.
The SP7685 also has two modes of operation to control the output current: the 1X
mode and 2X mode. Operation begins after
the enable pin EN receives a logic high, the
bandgap reference wakes up after 200μs,
and then SP7685 goes through a soft-start
mode designed to reduce inrush current.
The SP7685 starts in the 1X mode, which
The 2X mode is the charge pump mode
where the output can be pumped as high as
two times the input voltage, provided the
output does not exceed the maximum voltage for the SP7685, which is internally
limited to about 5.5V. In the 2X mode, as in
the 1X mode, the output current is regulated
by the voltage at the FB pin.
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
4
© 2006 Sipex Corporation
THEORY OF OPERATION
In the Torch mode, (Flash = GND) the Flash
pin is set to logic low and the SP7685 FB pin
regulates to 50mV output:
tion circuitry turns off the output switches
to prevent damage to the device. If the
temperature drops back down below 135
degrees Celsius, the part automatically
recovers and executes a soft start cycle.
VFB = 50mV (Torch Mode)
When in Flash mode, (Flash = VIN), the FB
regulation voltage is set by the resistor RSET
connected between the RSET pin and SGND
and the equation:
OVERVOLTAGE PROTECTION
The SP7685 has over voltage protection. If the output voltage rises above
the 5.5V threshold, the over voltage
protection shuts off all of the output
switches to prevent the output voltage
from rising further. When the output
decreases below 5.5V, the device resumes normal operation.
VFB = RSET * 14μA / 5 (Flash Mode)
Where 14μA is an internal regulated
current and 5 is an internal factor used to
scale the VSET voltage to the VFB voltage.
Typical values of RSET are 140KΩ to
35KΩ for a range of VFB = 400mV to
100mV in Flash mode.
OVERCURRENT PROTECTION
The over current protection circuitry monitors the average current out of the VOUT
pin. If the average output current exceeds
approximately 1.6 Amps, then the
overcurrent protection circuitry shuts off
the output switches to protect the chip.
The output current is then set in either Flash
or Torch mode by the equation:
IOUT = VFB / RSENSE
FLASH TIMEOUT PROTECTION
BRIGHTNESS CONTROL USING PWM
Due to the high currents typically available
in Flash mode, it is necessary to protect the
white LED from damage if left on too long.
The SP7685 has a timeout in Flash mode of
approximately 2.6 seconds after which it will
shut down operation. Operation will not
begin again in Flash mode until the Enable
pin or Flash pin have been set Low and then
High again.
Dimming control can be achieved by applying a PWM control signal to the EN pin.
The brightness of the white LEDs is controlled by increasing and decreasing the
duty cycle of the PWM signal. While the
operating frequency range of the PWM
control is from 60Hz to 700Hz, the recommended maximum brightness frequency
range of the PWM signal is from 60Hz to
200Hz. A repetition rate of at least 60Hz is
required to prevent flicker.
OVERTEMPERATURE PROTECTION
When the temperature of the SP7685 rises
above 145˚C, the overtemperature protec-
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
5
© 2006 Sipex Corporation
APPLICATION INFORMATION
VIN =3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
SP7685 Torch Output Current
300
SP7685 700mA Flash output Current
900
250
Output Current (mA)
Output Current (mA)
850
200
150
-40C
100
25C
85C
50
800
750
700
650
600
-40C
550
25C
500
85C
450
0
3.0
400
3.2
3.4
3.6
3.8
4.0
4.2
3.0
Input Voltage (V)
1000mA,Vf=3.31V PWF1
700mA,Vf=3.24V PWF1
700mA,Vf=3.92V AOT
200mA,Torch Mode
3.2
3.4
3.6
3.8
4.0
4.2
4.0
4.2
90
80
70
60
50
40
1000mA,Vf=3.31V PWF1
30
20
10
700mA,Vf=3.18V PWF1
700mA,Vf=3.92V AOT
200mA,Torch
0
3.0
3.6
SP7685 Output Efficiency
100
Efficiency (%)
Output Current (mA)
3.4
Input Voltage (V)
SP7685 Output Current
1100
1000
900
800
700
600
500
400
300
200
100
0
3.2
3.8
4.0
3.0
4.2
3.2
3.4
3.6
3.8
Input Voltage (V)
Input Voltage (V)
SP7685 VFB vs RSET
450
400
350
VFB (mV)
300
250
200
Measured
Calculated
150
100
50
0
10
20
30
40
50
60
70
80
90 100 110 120 130 140 150
RSET (KΩ)
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
6
© 2006 Sipex Corporation
APPLICATION INFORMATION
VIN =3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
EN
EN
VOUT
VOUT
VFB
VFB
IOUT
1A/div
IOUT
1A/div
Torch in 1X to Flash in 1X Mode, V IN=4.2V
Torch in 1X to Flash in 2X Mode, V IN=3.6V
EN
EN
VOUT
VOU
VFB
VFB
IIN
1A/div
IIN
1A/div
Start Up 1000mA Flash
VIN=3.6V, VOUT=3.8V
Start Up 200mA Torch
VIN=3.6V, VOUT=3.1V
EN
EN
VOU
VOUT
VFB
IIN
1A/div
VFB
Start Up 700mA Flash
V IN=3.6V, VOUT=3.6V
Date: 6/20/06 Rev T
Flash Mode TimeOut Circuit at 2.6sec.
VIN=4.2V, IOUT=1A
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
7
© 2006 Sipex Corporation
APPLICATION INFORMATION
VIN =3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
Input
Ripple
Input
Ripple
Output
Ripple
Output
Ripple
Ripple 1X Torch 200mA, V IN=4.2V
Ripple 2X Torch 200mA, V IN=3.0V
Input
Ripple
Input
Ripple
Output
Ripple
Output
Ripple
Ripple 1X Flash 700mA, V IN=4.2V
Ripple 2X Flash 700mA, V IN=3.6V
Input
Ripple
Input
Ripple
Output
Ripple
Output
Ripple
Ripple 1X Flash 1000mA, V IN=4.2V
Date: 6/20/06 Rev T
Ripple 2X Flash 1000mA, V IN=3.6V
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
8
© 2006 Sipex Corporation
COMPONENT SELECTION
RESISTOR SELECTION
The sense resistor RSENSE is determined by
the value needed in the Torch mode for the
desired output current by the equation:
The SP7685 charge pump circuit requires
three capacitors: 10μF input, 10μF output
and 1μF fly capacitor are typically recommended. For the input capacitor, a value of
10μF will help reduce input voltage ripple for
applications sensitive to ripple on the battery
voltage. All the capacitors should be surface mount ceramic for low lead inductance
necessary at the 2.4MHz switching frequency
of the SP7685 and to obtain low ESR, which
improves bypassing on the input and output
and improves output voltage drive by reducing output resistance. Ceramic capacitors
with X5R or X7R temperature grade are
recommended for most applications. A selection of recommended capacitors is included in Table 1 below.
Once the RSENSE resistor has been selected
for Torch mode, the VFB voltage can be
selected for Flash mode using the following
equation:
VFB = IOUT * RSENSE (Flash Mode) where IOUT is
for Flash Mode.
Part Number
Capacitance/
Voltage
CapacitorSize/
Type/Thickness
ESR
@100kHz
C1005X5R0J105M
C1608X5R0J475K
C2012X5R0J106M
GRM155R60J105KE19B
GRM188R60J475KE19
GRM21BR60J106KE19L
1uF/6.3V
4.7uF/6.3V
10uF/6.3V
1uF/6.3V
4.7uF/6.3V
10uF/6.3V
0402/X5R/0.5mm
0603/X5R/0.9mm
0805/X5R/1.35mm
0402/X5R/0.55mm
0603/X5R/0.9mm
0805/X5R/1.35mm
0.03
0.02
0.02
0.03
0.02
0.02
Manufacturer's Website
TDK: www.tdk.com
TDK: www.tdk.com
TDK: www.tdk.com
Murata: www.murata.com
Murata: www.murata.com
Murata: www.murata.com
RSENSE = VFB/ IOUT where VFB = 50mV (Torch
Mode)
Table 1: Recommended Capacitors
Next, the RSET resistor can be selected for
Flash mode using the following equation:
The input and output capacitors should be
located as close to the VIN and VOUT pins as
possible to obtain best bypassing, and the
returns should be connected directly to the
PGND pin or to the thermal pad ground located
under the SP7685. The fly capacitor should
be located as close to the C1 and C2 pins as
possible. See typical circuit layout at the end
of this section for details on the recommended layout.
RSET =
Ω (Flash Mode)
For an example of 200mA Torch mode and
700mA Flash mode, the values RSENSE =
0.22Ω, VFB = 155mV (Flash Mode), and RSET
=56KΩ are calculated. The power obtained
in the Flash mode would be:
To obtain low output ripple, a value of 10μF
is recommended for COUT. For output currents of 500mA to 1.2A, the recommended
CFC fly capacitor value of 1μF should be
used. Output currents in Flash of 100mA to
400mA can use a 0.47μF CFC but a minimum
4.7μF COUT is still needed.
Date: 6/20/06 Rev T
VFB
(14uA )* 5
PFLASH = VFB *IOUT = 155mV*700mA = 109mW.
The typical 0603 surface mount resistor is
rated 1/10 Watt continuous power and 1/5
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
9
© 2006 Sipex Corporation
COMPONENT SELECTION
mended to be size 0603 for most applications. The range of typical resistor values
and sizes are shown here in Table 2.
Watt pulsed power, more than enough for
this application. For other applications, the
PFLASH power can be calculated and resistor
size selected. The RSENSE resistor is recomPart Reference
RSET
RSET
RSET
RSET
RSET
RSET
RSET
RSET
RSET
RSET
RSET
RSET
RSENSE
RSENSE
RSENSE
RSENSE
RSENSE
RSENSE
RSENSE
Value
33kΩ
39kΩ
43kΩ
47kΩ
56kΩ
62kΩ
68kΩ
82kΩ
100kΩ
110kΩ
120kΩ
150kΩ
0.22Ω
0.27Ω
0.33Ω
0.39Ω
0.47Ω
0.56Ω
0.68Ω
Tolerance
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
105%
205%
Size
0402
0402
0402
0402
0402
0402
0402
0402
0402
0402
0402
0402
0603
0603
0603
0603
0603
0604
0605
Manufacturers
any
any
any
any
any
any
any
any
any
any
any
any
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Table 2: Resistor values and sizes
EVALUATION BOARD CIRCUIT LAYOUT
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
10
© 2006 Sipex Corporation
PACKAGE: 10 PIN DFN
D
D/2
ø
E/2
A
(A3)
E
A1
Seating Plane
SIDE VIEW
Pin1 Designator
to be within this
INDEX AREA
(D/2 x E/2)
TOP VIEW
D2
D2/2
1
2
3
4
5
INDEX AREA
(D/2 x E/2)
E2/2
E2
K
L
10
9
8
7
e
6
b
BOTTOM VIEW
3x3 10 Pin DFN
SYMBOL
JEDEC MO-229
Dimensions in Millimeters:
Controlling Dimension
NOM
0.90
0.02
0.20 REF
0.20
0º
b
0.18
0.25
D
3.00 BSC
D2
2.20
E
3.00 BSC
E2
1.40
e
0.50 BSC
L
0.30
0.40
SIPEX Pkg Signoff Date/Rev:
A
A1
A3
K
ø
Date: 6/20/06 Rev T
MIN
0.80
0.00
MAX
1.00
0.05
14º
0.30
2.70
1.75
0.50
VARIATION VEED-5
Dimensions in Inches
Conversion Factor:
1 Inch = 25.40 mm
MIN
NOM
MAX
0.032
0.036
0.039
0.000
0.001
0.002
0.008 REF
0.008
0º
14º
0.008
0.010
0.012
0.119 BSC
0.087
0.106
0.119 BSC
0.056
0.069
0.020 BSC
0.012
0.016
0.020
JL Aug09-05 / RevA
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
11
© 2006 Sipex Corporation
ORDERING INFORMATION
Part Number
Operating Temperature Range
Package Type
SP7685ER-L ............................................... -40°C to +85°C ....................................... (Lead Free) 10 Pin DFN
SP7685ER-L/TR ........................................ -40°C to +85°C ....................................... (Lead Free) 10 Pin DFN
/TR = Tape and Reel
Pack quantity is 3,000 for DFN.
Sipex Corporation
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the
application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
12
© 2006 Sipex Corporation